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New LIDAR Instrument Lets Volcanologists Monitor Eruptions from Afar

11 April 2017

Recent studies suggest that before a volcano erupts, it ramps up its release of carbon dioxide from magma deep below the surface. These fluxes may provide an important early warning signal that an eruption is imminent. Researchers can measure volcanic gases using sampling instruments, but they must install these devices at the rim of the crater, placing both themselves and the instrument at risk.

Alessandro Aiuppa, along with fellow Reservoirs and Fluxes Community members Roberto D’Aleo (both of the Università di Palermo, Italy), Marco Liuzzo and Gaetano Giudice (both of the Istituto Nazionale di Geofisica e Vulcanologia, Italy), and colleagues from ENEA (Agenzia Nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile), have developed a new generation of instruments to measure volcanic gases remotely. They successfully used a type of laser scanning technology called LiDAR to measure carbon flux at Stromboli volcano, described in a paper in Frontiers in Earth Science [1], and at Mt. Etna, published in a study in the journal Geosciences [2]. The work receives funding from the ERC (European Research Council) BRIDGE project and is in collaboration with DECADE (Deep Earth Carbon Degassing), a DCO initiative to estimate the global release of volcanic carbon by monitoring some of Earth’s most active volcanoes.

“Using gas chemistry, you can probe the deepest part of the volcano,” said Aiuppa. “Our goal is to develop new techniques for real-time observation of volcanic gas composition in an attempt to interpret and possibly forecast volcanic activity. This new technology is helping us get another step closer.”

The studies report on the novel use of LiDAR for measuring carbon dioxide from volcanoes remotely. This task has proven particularly challenging because carbon dioxide makes up 0.04 percent of the atmosphere. Researchers have had difficulty detecting small changes above background levels. The new technology relies on lasers, set to a wavelength absorbed by carbon dioxide, that scan the volcanic plume. Researchers can then determine the concentration of the gas based on how much light reflects back to the instrument, after it bounces off water vapor and other particles.

The researchers deployed their DIAL-LiDAR (Differential Absorption Light Detection and Ranging), three kilometers from Stromboli volcano in June 2014 and four kilometers from Mt. Etna in July 2016 to record carbon dioxide levels in the plumes. The resulting estimates of carbon dioxide flux are in good agreement with previous estimates and with automatic multi-GAS instruments taking measurements at the crater’s rim made at the same time.

The studies provide proof of concept that LiDAR can be used to monitor volcanic gases more safely than existing instruments. The new technology also collects data more frequently, providing better resolution of gas fluxes, and yields results quicker than previous methods.

While the results from the prototype are very promising, the instrument is not yet ready for routine use. The researchers hope to shrink the instrument so that it will be more portable and require less energy to run. They also plan to make it easier to use and less expensive to operate.

Ultimately, future versions of the DIAL-LiDAR system may provide safe and accurate long-term volcano monitoring to give communities days or even weeks of warning before a volcano erupts. The technology can also give more accurate estimates of volcanic carbon release.

While the researchers have observed a bump in carbon emissions before eruptions with all of the volcanoes they have studied, Aiuppa still wants to confirm these findings at additional sites.

“We still need to improve our ability to measure volcanic emissions and we still need to expand our measurement network,” said Aiuppa. Currently, researchers measure gas emissions systematically at 12 volcanoes in Europe, Central America, and South America, but with the help of DCO’s DECADE, that number should grow to 20 by 2019.

Scientists transport the DIAL-LiDAR system by mounting it in a trailer loaded onto a truck. Credit: Photo provided by Alessandro Aiuppa

The BILLI DIAL has a clear view of Mt. Etna’s volcanic plume from the Pizzi Deneri observatory. Credit: Photo provided by Alessandro Aiuppa

The Deep Carbon Observatory (DCO) is a global community of multi-disciplinary scientists unlocking the inner secrets of Earth through investigations into life, energy, and the fundamentally unique chemistry of carbon.